Studies on the little known redox properties of aromatic cations from N-acyloxypurines in the presence of "soft" base nucleophiles and carcinogenesis protective agents show that both the type and degree of direct interaction between protective agents and electrophilic intermediates from "activated" esters of oncogens can be determined in vitro. This information can indicate which protective agents might be effective against a particular oncogen in vivo and the concentration needed for protection. Work will now be extended to the study of additional types of nucleophiles and protective agents as well as to the "activated" forms of other types of arylamine oncogens. Information gained from those studies will be used to design more effective carcinogenesis protective agents. New agents will be evaluated by examining their ability to protect against mutagenesis in cell culture.